Reliability and validity of a new dexterity questionnaire (DextQ-24) in Parkinson's disease

BACKGROUND: Patients with Parkinson's disease exhibit disturbed dexterity. Validated self-reported outcomes for dexterity in Parkinson's disease are lacking. The aim of this study was to investigate the reliability, content and construct validity of a new Dexterity Questionnaire 24. METHODS: One hundred and three patients with Parkinson's disease completed the Dexterity Questionnaire 24 (score range 24-96), at baseline and four weeks later. The internal consistency was determined. Test-retest reliability was assessed in a subgroup (N = 44). Standard error of measurements and the minimal detectable change were defined. The construct validity was examined in the whole group (N = 103). Floor and ceiling effects were investigated. RESULTS: The internal consistency of the Dexterity Questionnaire 24 was high (α = 0.91). High test-retest reliability was found (Intra Class Correlation Coefficient = 0.91, Confidence interval: 0.84-0.95). Standard error of measurement was 2.9 and minimal detectable change was 8 points. (i.e., 11%). Good structural, convergent and divergent validity of the Dexterity questionnaire 24 was found (r = 0.73 with Activities of Daily Living-subscale of the Parkinson's Disease Questionnaire-39, and r = 0.66, and r = 0.50, p-values all < 0.0001, respectively with the subscales II and III of the Movement Disorders Society-Unified Parkinson Disease Rating Scale). Low not significant correlations were found between the Dexterity Questionnaire 24 and the subscales stigma and social support (r = 0.20, and r = 0.14 respectively). No floor or ceiling effects were found for the total Dexterity Questionnaire 24. CONCLUSION: The Dexterity Questionnaire 24 is valid and reliable for evaluating dexterity in patients with Parkinson's disease